Back up just incase, but when you finish the jailbreak, 99.9999% of the time all your stuff is still there so no worries. Don't worry about blobs, that's if you need to go to a previous software version for some reason.
When you finish the jailbreak, go to your last screen and you'll see a "Load" application. Go into it, download Cydia, exit the app and your device will reboot. Then go into the Loader app, hit the Settings button and Remove Loader.app. Exit the app, reboot, and you're good to go.